This invention relates to cutting tools for milling and chasing threads, and to indexable inserts especially suited for such service.
Thread milling typically employs a milling cutter having a plurality of registering thread-profile cutting edges which are rotated about the cutter axis while the cutter makes a single orbit of the workpiece and advances axially through one thread lead to make a continuous thread one lead longer than the overall length of the cutting edge profile. In thread milling, each cutting edge repeatedly engages the workpiece for a relatively short time so that the complete thread is produced by a large number of relatively short cuts.
In thread chasing on the other hand, a series of superimposed continuous cuts of progressively greater depth is made along a helical path by a non-rotating cutter which is moved axially of the rotating workpiece with each cutting land of the cutting edge traversing the entire helical path.